Semi-trailer



FIG. 1 is a perspective view of a semi-trailer showing our new design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a rear elevational view thereof; and

FIG. 5 is a front elevational view thereof.

The broken lines in the drawing are for illustrative purposes only. 

The ornamental design for a semi-trailer, as shown and described. 